1. Field of the Invention
The present invention relates to an operation button fixing structure of an electric device.
2. Related Art
Electric devices have buttons necessary for operation on their fronts. Such a button is operatively connected to a switch in the circuit board, so that when the button is depressed, it may make the associated switch turn on or off. The circuit board is mounted on the chassis of the electric device. When fixing the operation button to the front panel of the electric device, the operation button needs to be aligned with the switch, which is fixed to the circuit board. Exact alignment is required, and therefore there has been an ever-increasing demand for making it easy to fix operation buttons to the front panels in exact alignment with the associated switches.
To meet such demand JP7-141961(A) discloses an “Operation button Mounting Structure” where an operation button to be pressed has a hook piece integrally to be caught with its front panel of the cabinet and the front panel has a counter hook to catch the hook piece at its rear side. The operation button is fixedly held on the rear side of the front panel by engaging the hook of the button with the counter hook of the front panel. The operation button can be easily fixed to the front panel, but it can be unhooked to come off from the front panel.
FIG. 6 shows another conventional operation button fixing structure. As shown, an operation button unit 1 is fixed to the rear side of the front panel 2 of the cabinet The front panel 2 has four tapped bosses 4 integrally connected to its rear side, and the operation button unit 1 is fastened to the four tapped bosses 4 by screwing the four corners of a frame 3. Thus, the frame 3 is apart from the rear side of the front panel 2 by the distance equal to the length of the boss 4.
The operation button unit 1 has two button assemblies 5, 5 encircled by its frame 3, and each button assembly 5 is connected to the frame 3 via hinge 6. Each button assembly 5 has an arm 8 extending backwards until its free end comes to contact with an associated switch 10, which is mounted on a circuit board 9. When either button assembly 5 is depressed, its arm 8 inclines about the hinge 6 to push the associated switch 10 with its free end.
FIG. 7a is a rear view of the front panel 2 having the operating button unit 1 mounted on its rear side; FIG. 7b is a sectional view of the front panel-and-operation button combination taken along the line 7b —7b in FIG. 7a; and FIG. 7c is another sectional view of the front panel-and-operation button combination taken along the line 7c—7c in FIG. 7a. As seen from these drawings, the frame 3 is screwed to the bosses 4, which project backwards from the rear side of the front panel 2. Each button 11 projects forward from the upright base piece 7 of the button assembly 5, passing through the hole 12 made in the front panel 2. As seen from FIGS. 7b and 7c, the button 11 partly appears from the front side of the front panel 2. With this arrangement, when the button 11 is depressed, the upright base piece 7 is yieldingly inclined about the hinge 6 to make the arm end contact with the switch 10.
As the operation button unit 1 is screwed to the rear side of the front panel, it cannot come off from the front panel. The operation button, however, cannot be fixed to the front panel with ease. FIG. 8 illustrates how the operation button 1 can be fixed to the rear side of the front panel 2, and how the circuit board 9 can be fixed to the bottom plate of the cabinet of the electric device. First, the operation button 1 is screwed to the front panel 2, and then, the circuit board 9 is fixed to the bottom plate (chassis). In the example shown in the drawing, four screws are used in fixing the operation button 1 to the front panel 2. The number of screws will increase with the increase in the number of the operation buttons to be fixed to the rear side of the front panel 2, and accordingly, the fixing work will be increasingly tedious. Further, the fixing work with use of screws will be more tedious and difficult when the space between the operation buttons and the bottom plate is narrow in an electric device such as a television.
In view of the above, one object of the present invention is to provide an operation button fixing structure which is capable of readily fixing an operation button to the front panel without fear of loosening and coming apart from the front panel.